Method and apparatus for sampling

ABSTRACT

There is provided a method and apparatus for sampling a viscous liquid by aspiration of such liquid from a container in an offtake tube of a probe insertable in the container. A reagent having the characteristic of a solvent is added to the sample to dilute it within the probe after a relatively short distance of travel of the sample within the probe. The reagent is fed into the probe at a first predetermined flow rate and the admixture is aspirated at a second predetermined flow rate which is faster so that the sample is aspirated at a rate determined by the difference between the first and second flow rates.

United States Patent [15] 3,668,936 Herron [4 1 June 13, 1972 [5 METHODAND APPARATUS FOR 3,186,235 6/1965 Ferrari ..73/432 SAMPLING v PrimaryExaminer-S; Clement Swisher [72] Inventor. Rand E. llerron, Stamford,Conn. Atmmey Tedesco & Rockwell [73] Assignee: Technicon InstrumentsCorporation, Tarrytown, N.Y. [57] ABSTRACT [22] Filed: Dec- 15, 1970There is provided a method and apparatus for sampling a 1 viscous liquidby aspiration of such liquid from a container in [21] Appl 98365 an ofitake tube of a probe insertable in the container. A reagent having thecharacteristic of a solvent is added to the [52] US. Cl. ..73/423A le todil te it within the probe after a relatively short [51] 'P- Golh 1/14distance of travel of the sample within the probe. The reagent [58]Fleld of Search ..73/423 A, 421 B; 356/244, 246; is fed into the probeat a first predetermined flow rate and the 23/253 admixture is aspiratedat a second predetermined flow rate which is faster so that the sampleis aspirated at a rate deter- [56] R g Cited mined by the difierencebetween the first and second flow UNITED STATES PATENTS 2,899,280 8/ l959 Whitehead et al ..23/230 I 3 Claim, 3 Drawing Figures T0 ANALYSISHG. i

PATENTEDJuu 1 3 m2 PEG. 3

INVENTOR RAND E. HERRON T N E G A E R FIG. 2

ATTORNEY METHOD AND APPARATUS FOR SAMPLING BACKGROUND OFTHE INVENTION 1.Field of Invention This invention relates to a method and apparatus forsampling liquids for automated continuous analysis and especially to atechnique for achieving a particular flow of such liquid in asampleprobe.

2-. Prior Art Apparatus for the. continuous'analysis of fluids are wellknown. Such an apparatus is disclosed in U.S. Pat. No.

2,797,149 issued June 25, 1957. US. Pat. No. 2,879,141 is specimen foranalysis in a flame, for example, employing a spectrophotometer.Heretofore, attempts have been made to utilize such apparatus forquantitative analyses of trace amounts-of what is known as wear metals"in lubricating oil samples which have been taken from sources of usedoilsuch as sumps of internal combustion engines or other types of en--gines for example, after a period of engine operation, to determinewear of lubricated metal engine parts by the presence in the oil ofundue amounts of one or more kinds of metal. The presence of metal invery small amounts is usually normal and can be expected. e

Such analyses are made for the purpose of determining whether or not anengine is in need of reconditioning or inspection of parts bydisassembly. Cumulative amounts of wear metal in a series of lubricatingoil samples taken from a single engine may be indicative of the amountof wear of an engine part or parts, especially when such tests are maderepeatedly over a period of time of engine operation so as to give anengine history.

Metal of certainkinds found in such oil may indicate particular engineareas requiring at least inspection for wear. For example, iron in suchoil may indicate wear of an iron camshaft, while the presence ofchromium may indicate wear of chromium piston rings. The detection ofunusually large amounts of aluminum in such oil indicates wear of partsconstructed of such metal.

Known prior attempts at automated quantitative analyses of wear metalshave been largely unsatisfactory because such tests gave impreciseresults of measurements of metal present in such oil. The imprecision ofsuch prior attempts at automated quantitative determinations'was in therange of percent of the wear metal. This degree of inaccuracy ofmeasurements made valid determinations as to whether or not an enginerequired an overhaul difficult at best.

As is well known, lubricating oil is used, as in engines, in varyingviscosities. Oil samples from different enginesmay have quite differentviscosities, and for this reason may flow at quite different rates in ananalysis system wherein pressure is employed to induce flow in thesystem of liquid samples and reagents. More particularly, for a givenaspiration time, more of a light oil would flow into an analysis systemas from a sample cup through an off-take device than would a heavier ormore viscous oil. This difference in flow of oil samples in such asystem made for inaccurate test results.

SUMMARY OF THE INVENTION 7 It is an object of the invention to providean improved method and apparatus for sampling of viscous liquids byaspiration of such liquid from a container through an off-take 7 deviceinsertable in the latter. A further object is to provide apparatus,making possible more precise quantitative determinations of trace metalspresent in the samples.

A further object is to provide an improved probe structure in a sampleoff-take device for use in sampling viscousliquids which may be thinnedby the addition of a solvent within the probe structure so as to flowmore readily therein and in the remainder of the analysis apparatus,which addition is made after a very short distance of travel of' thesample within the probe structure. It is an object of the invention toprovide for the dilution of a liquid sample, such as lubricating oil, asby the addition thereto in a sample probe structure near the sampleinlet of a reagent such as caprylic alcohol. This enables the use in ananalysis system for determiningwear metal in oil of a peristalticproportioning pump for causing samples and reagents to flow in thesystem. I

Still another object of the invention is to provide a probe structureincluding a outer tube vertically arranged and having at its upper endan inlet for reagent, and an inner sample tube axially arranged, ofsubstantially smaller outer diameter than the internal diameter of thefirst-mentioned tube, extending through a bottom seal of the outer tube.The inner tube has a lower inlet end for sample and an upper outlet endwithout the outer tube. Within the confines of the outer tube, the innertube is provided with communication between the interior thereof and theinterior of the outer tube in a location in proximity to the bottom ofthe latter. Reagent is flowed into the outer tube inlet at a firstpredetermined flow rate and the admixture is aspirated through theoutlet of the inner tube at a second predetermined flow rate which isfaster, so that the sample is aspirated through the lower inlet end ofthe inner tube at a rate determined by the difference between the firstand second flow rates.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a somewhat diagramatic view illustrating apparatus forsampling liquids, embodying the invention, and showing the sameconnected to a portion of an analysis system;

FIG. 2 is an enlarged fragmentary view in elevational section,illustrating the sample off-take device of the invention including aprobe; and

FIG. 3 is a fragmentary view, partially in elevational section,illustrating the use of the sample off-take device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 there is illustrateda sampler, indicated generally at 10, for supporting a plurality ofliquid samples; a sample offtake device at 11 including a sample probe;a pump of 12 for aspirating sample and reagent, shown connected to theolftake device 11; and an ultrasonic mixer at 13 connected to the pumpdownstream from the latter, which mixer is located upstream of analysiselements not shown which may include a conventional flame device and aspectrophotometer.

The sampler includes (FIG. 3) the usual turntable 14 provided with aseries of sockets circumferentially spaced from one another, one beingindicated at 14A, to removably receive respective sample cups, one beingindicated at 15. The respective sample cups 15 may contain differentsamples of lubricating oil containing trace amounts of wear metal, thatis, samples from different sources, such as previously described, and ofvarying viscosities. The sampler includes a stationary coverplate 16having an aperture 17 (FIG. 3) which registers with a sample cup indexedby the turntable 14 at an off-take station. Here sample is withdrawnfrom the indexed sample cup.

As shown in FIG. 3, the off-take device 11 is mounted for movement onone end of a horizontal arm 18 the other end of which is fixed to an endof a vertical shaft 19. The shaft 19 swings about a horizontal axis toraise and lower the off-take device, and the construction of the samplerand the mechanism for moving the off-take device 11 may be similar tothat shown and described in Isreeli U.S. Pat. No. 3,251,229 issued May17, 1966, so as not to require further description here. The off-takedevice 11 is lowered into and raised from an indexed sample cup 15. Whenit is in raised position, the off-take device aspirates air and, betweensamplings from neighboring cups, may be lowered into a stationaryreceptacle of wash liquid to aspirate a quantity of such liquid, all asdescribed in the last-mentioned patent. If desired, the mechanism tomove the off-take device into and out of the sample cup may be differentin character and in accordance with Isreeli U.S. Pat. No. 3,038,340issued June 12, 1962 or de long U.S. Pat. No. 3,134,263 issued May 26,1964, by way of example.

It is to be understood from the foregoing that the off-take device ismounted for movement of the same into and out of the sample cups for theflow of the sample liquids from the receptacles automatically fortreatment for analysis and analysis after such treatment. The turntable14 of the sampler is operated intermittently to bring the sample cups insuccession to the off-take station.

The off-take device comprises an outer tube which is vertically arrangedand which is structured of a corrosion resistant metal. This tube may beof cylindrical cross section. As shown in FIG. 2 the tube 20 passesthrough the distal end portion of the previously described support arm18 and is suitably secured thereto so as to prevent axial dislocation ofthe tube. Above the arm, the tube 20 is provided with an enlarged upperend cap or seal 21 which is shown as abutting the upper surface of thesupport arm 18. The seal 21 may be integrally formed as part of thetube. In the region of the last-mentioned seal the tube 20 is providedwith a fluid inlet, including a tube 22, which extends laterally intocommunication with the upper end portion of the interior of the tube 20.The lower end of the tube 20 has a cap or seal 23 which may be formedintegrally therewith and through which an inner tube 24 extends.

The inner tube 24, which may be structured of a material similar to thatof the outer tube, extends axially of the tube 20 beyond theaforementioned end seals thereof and is shown as having the portionthereof within the tube 20 concentrically arranged. The tube 24, whichmay be of cylindrical cross section, has an outer diameter substantiallysmaller than the inner diameter of the tube 20 to form a chamber 25therebetween which extends between the end seals 21 and 23. Theaforementioned end seals may support the tube 24 to prevent axialmovement thereof with reference to the tube 20.

The illustration of the off-take device in FIG. 2 is many times largerthan the actual device presently contemplated. By way of example theinner tube 24 may have an inner diameter of 0.034 inch and an outerdiameter of 0.050 inch and the outer tube 20 may have an inner diameterof 0.79 inch and an outer diameter of0.095 inch.

As shown the extension of the inner tube 24 in a downward directionbeyond the end seal 23 is straight and vertically arranged, and thelower end 26 ofthe tube 24 is open to provide a sample inlet. Upwardlybeyond the end seal 21, the tube 24 has an outlet end beyond a laterallydirected portion 27 of the last-mentioned tube.

Within the confines of the outer tube 20 but spaced upwardly only ashort distance from the lower end seal 23, the inner tube 24 is providedwith a transverse opening 28 extending completely therethrough and incommunication with the interior of the tube 24, forming diametricallyopposite inlet ports which may be cylindrical. The last-mentioned portsare horizontally arranged and aligned. A similar opening 29, also withinthe confines of the outer tube 20, located intermediate the opening 28and the end seal 23, is formed in the inner tube 24 to provide anadditional pair of inlet ports on a lower horizontal plane but close tothe opening 28. The openings 28 and 29 have their axes arranged invertical planes which cross one another at right angles.

It is important in the use of the off-take device for samplinglubricating oil from sources of varying viscosities that thelastmentioned inlets in the tube 24 within the confines of the tube 20be located in relatively close relationship to the sample inlet end 26of the inner tube for reasons which will be apparent from the subsequentdescription of the operation of the off-take device for such sampling.By way of example the distance of the opening 29 in the tube 24 abovethe inlet end 26 of the last-mentioned tube may be approximately 0.40inch.

During each rest period of the sampler turntable 14, the sample liquidis aspirated from the indexed sample receptacle at the ofi-take stationby the pump 12 which, as shown in FIG. 1, includes resilientlycompressible tubes 30, 32 connected respectively to fluid inlet tube 22and fluid outlet 27 of the offtake device. Pump 12 may be of theconstruction shown in Smythe U.S. Pat. No. 3,306,229 issued Feb. 28,1967. As shown diagramatically in FIG. 1, the pump comprises a pluralityof compression rollers 34 in laterally spaced apart relation havingtheir respective ends supported by a pair of parallel spaced-apartsprocket chains 36. The pump comprises a platen 38 against which aplurality of compressible tubes, including the tubes 30 and 32, aresimultaneously compressed progressively along their lengths by thecompression rollers 34 which are moved in an endless path longitudinallyof the pump tubes by the sprocket chains 36.

While the pump is in operation, a reagent from a suitable source, notshown, is flowed in pump tube 30 to inlet 22 of the off-take devicewhere it enters chamber 25 between the aforementioned tubes 20, 24,filling the chamber before the commencement of a sampling operation. Thereagent flows into the off-take tube 24 through the ports 28, 29 formixture with a sample in the last-mentioned tube when the latter isimmersed in a liquid sample and the sample is drawn upwardly in theoff-take tube 24. The multidirectional ports 28, 29 in the tube 24 makepossible even dilution of the sample within the tube 24, and preventsurging of liquid within the last-mentioned tube. The dilution of thesample is continuous and made at a substantially constant rate. Thesample is drawn upwardly in the tube 24 through the sample inlet end 26of the tube, traveling only a short distance in the tube before theadmixture therewith of the reagent. The mixture then passes upwardly inthe tube 24 beyond the last-mentioned ports and through the outlet 27 ofthe off-take tube 24, flowing into pump tube 32. The sample is aspiratedby the difference in the flow rates in the tubes 30, 32. For example,the flow through the tube 30 to the reagent inlet 22 may be 2.0 ml/min.while the flow through the tube 32 may be 2.5 ml/min., causing thesample to flow at the difference of 0.5 ml/min. and diluting the sampleat a ratio of4: 1. For this purpose the pump tube 32 has a largerinternal diameter than the pump tube 30.

Also during the operation of the pump, air or inert gas or otherimmiscible fluid may be caused to flow in pump tube 40 to join thesample-reagent mixture as at the junction 42. This use of an immisciblefluid segments the sample-reagent stream. This segmentation is for thepurpose of maintaining sample integrity and cleansing of the tubingwalls. The immiscible fluid may also segment portions of each liquidsample. The segmented sample-reagent stream is caused to flow from thepump 12 to the ultrasonic mixer 13 from which it flows for analysis. Ifdesired, the diluted sample may be mixed by means other than theultrasonic mixer 13. Instead, mixing may be accomplished utilizing oneor more coils in which the diluted sample is transported towardanalysis.

Mixture of a solvent with a sample of lubricating oil in the tube 24near the sample inlet 26 reduces the viscosity of the oil in theoff-take device to render samples of oils of different viscosities of amore uniform viscosity within the tube 24 and more uniformly flowable inthe latter and through the pump on aspiration of the sample for properproportioning by the pump 12. The short distance of travel of theundiluted lubricating oil in the off-take tube 24 prior to being mixedwith a solvent does not significantly affect the flow rate of thesample. The reagent used for the above described purpose isadvantageously caprylic alcohol.

Polyvinyl chloride has been employed as a material for pump tubing, andcaprylic alcohol does not have such a corrosive affect on this tubing asother known solvents, which is one of the advantages of use of suchalcohol as a diluent. Other solvents tried as diluents attacked all pumptubes tried for use on peristaltic type pumps. Such corrosive attacksrendered such pump tubes unusable. Hence, such pumps were not usableunder these conditions. The combination of use of caprylic alcohol as adiluent with polyvinyl chloride pump tubing has worked well, and use ofthis diluent has also not interferred with the stability of a flame usedin conjunction with a spectrophotometer. Other types of solvents havebeen observed to create unstable flames resulting in less satisfactoryperformance of analyses. It is to be understood that among the apparatuselements not shown may be a digital printer or a conventional recorderhaving operative connections from a spectrophotometer and having adriven stylus for cooperation with conventional chart paper to provide arecord of the quantitative analysis of each of the samples in successionin the stream of sample liquids during the operation of the apparatus.

As previously indicated, the segmented sample-reagent stream on leavingthe pump 12 may be introduced into the ultrasonic mixer 13 beforecontinuing to flow to one or more stages for analysis. This mixer iscapable of mixing the constituents of each liquid slug withoutdisturbing the segmentation of the stream as by air bubbles. The mixerincludes an upright walled container 44 which may be open at the top andserve as a receptacle receiving, among other things, a liquid up to aheight similar to that shown in FIG. 1. The liquid may be water and thecontainer 44 may have a water inlet 46 and a water outlet 48 so thatwater may be circulated through the container so as to maintain arelatively low temperature or inhibit an undue rise of water temperaturein the operation of the mixer.

A suitably supported ultrasonic transducer, indicated generally at 50,is immersed in the liquid as shown, having an upwardly extending arm 52in which an electrical lead 54 extends. A tubular coil 56 having one endthereof receiving the segmented sample-reagent stream downstream fromthe pump, as from the fitting 42, has the other end thereof connected tothe one end of a tube 58 extending toward the analysis portion of theapparatus in the manner indicated in FIG. 1. The coil 56 may becompletely immersed in the liquid in the container 44 but in the formshown it is only partially immersed therein. Ultrasonic mixing powerfrom the transducer penetrates the wall structure of the coil to produceeffective mixing, with the liquid in the container 44 acting as acoupling medium for this power while also serving as a cooling mediumthrough circulation thereof.

When the off-take device 11 is raised, as from a sample cup, so that theinlet end 26 of the off-take tube 24 is suspended in the atmosphere, airis aspirated into the inlet end 26 of the 'tube 24, mixing with reagentflowing into the tube 24 from the tube through the bores 28, 29. Thismixture is aspirated into pump tube 32 from the tube 24. When the inletend 26 of the off-take tube 24 is immersed in wash liquid in the mannerpreviously described, the wash liquid flows into the aforementionedinlet of the tube 24, and as it is aspirated in the tube mixes withreagent flowing into the last-mentioned tube through the ports 28, 29.This flow of aforementioned mixed fluids between sampling intervalscleans the tubing walls with the aid of the immiscible fluid introducedinto the fluid stream from the pump tube 40, and in this mannercontamination of one sample by another is prevented.

It has been noted previously that each liquid sample is diluted near itspoint of entry into the conduit system of the analysis apparatus by theaddition of a large proportion of diluent as by mixing one part of thesample to four parts of the diluent. This amount of dilution oflubricating oil samples of different viscosities renders the differencesin sample viscosities relatively small so that substantially the sameamount of sample may be taken off from every sample container in thesame flow period.

In the use of the above described apparatus, precision of quantitativedeterminations of trace amounts of wear metal in lubricating oil hasbeen greatly improved. With this improved method, determinations havebeen made which are precise within an average of 10.5 percent of thewear metal present in oil. Precision within 0.27 to 1 percent of theamount of iron present in such oil has been developed using thistechnique. It will be appreciated that the method and apparatus may beuseful in analyses of other liquids and substances.

It is believed the many advantages of this invention will now beapparent to those skilled in the art. The foregoing description isillustrative, rather than limiting, as a number of variations andmodifications may be made without departing from the true spirit andscope of the invention. The invention is limited only by the scope ofthe following claims.

What is claimed is: i

l. A method of treating a series of liquid samples for analysis, whichsamples have viscosities substantially greater than that of water anddiffering one from another, utilizing a sample probe immersible in suchsample liquids successively and having a sample inlet and according towhich the samples and a solvent liquid and a gas are transmitted in theform of a flowing stream in a first conduit connected to said probe andaccording to which said gas is effective to divide said stream into aseries of spaced liquid segments separated from each other byintervening segments of gas, comprising: immersing said probe in suchsamples successively, flowing each such sample liquid into the probewhile the latter is in the immersed condition through said inletthereof, flowing said solvent liquid in a second conduit, flowing saidgas in a third conduit, and concurrently introducing continuously saidsolvent liquid into the sample liquid in said probe in proximity to saidinlet prior to the segmentation of said stream by said gas, so that theviscosity of the sample liquid is lessened for flow through said probeand said first conduit and the formation of said liquid segments occursafter the introduction of said solvent liquid, whereby the sampleliquids flowing in said probe and in said first conduit tend to haveuniform viscosities one to another.

2. A method as defined in claim 1, wherein: each sample liquid consistsof lubricating oil.

3. A method as defined in claim 1, wherein: each sample liquid islubricating oil bearing trace amounts of wear metal and the solventliquid is caprylic alcohol.

1. A method of treating a series of liquid samples for analysis, whichsamples have viscosities substantially greater than that of water anddiffering one from another, utilizing a sample probe immersible in suchsample liquids successively and having a sample inlet and according towhich the samples and a solvent liquid and a gas are transmitted in theform of a flowing stream in a first conduit connected to said probe andaccording to which said gas is effective to divide said stream into aseries of spaced liquid segments separated from each other byintervening segments of gas, comprising: immersing said probe in suchsamples successively, flowing each such sample liquid into the probewhile the latter is in the immersed condition through said inletthereof, flowing said solvent liquid in a second conduit, flowing saidgas in a third conduit, and concurrently introducing continuously saidsolvent liquid into the sample liquid in said probe in proximity to saidinlet prior to the segmentation of said stream by said gas, so that theviscosity of the sample liquid is lessened for flow through saId probeand said first conduit and the formation of said liquid segments occursafter the introduction of said solvent liquid, whereby the sampleliquids flowing in said probe and in said first conduit tend to haveuniform viscosities one to another.
 2. A method as defined in claim 1,wherein: each sample liquid consists of lubricating oil.
 3. A method asdefined in claim 1, wherein: each sample liquid is lubricating oilbearing trace amounts of wear metal and the solvent liquid is caprylicalcohol.